POF: What Am I Doing Wrong?

I'm newish to affiliate marketing. I've run some campaigns before but never made a profit. The general course runs like this: I'll get excited about an offer; put up ads; then test images, headlines, copy, and demographics; get low CTR and conversions; get discouraged, and give up on it.

So now, I'm running a new offer, and it's heading in that same direction again. I'd like to stick with this one and not give up so easily, but I honestly don't know what I'm doing wrong. Any advice would be appreciated. Here's some info on my current offer:

It's for a download, so it's not a dating ad. I'm promoting it on POF, CPM I tested at .3 and .5; gotten around 250,000 impressions, 140 clicks, and only 6 conversions. I've spent around $100 testing it (is this too low?). Tested around 15 images, 5 ad copies, and 6 different headlines. I know this is a top converting offer, so I don't think the low conversions is due to the offer. Is it just a matter of testing more? What do you think I should do?